1. Field of the Invention
This invention relates to a method of oxide hardmask aluminum etching in metal dry etch processors. It consists of two steps: the step of dry etching an aluminum interconnect stack (typically TiN) by using an etch gas composed mainly of boron trichloride/chlorine/fluoroform/nitrogen, and the step of removing etch remnants by using a water vapor plasma. The function of the etch gas is to etch the aluminum interconnection pattern in the semiconductor, and the function of the water vapor plasma is to prevent the corrosion of a chip during the process of removing etch remnants, which will further reduce water rinsing and solution cleaning as in conventional practice, of water rinsing and solution cleaning after removal of photoresist.
2. Description of the Related Art
In a conventional metal interconnection method, the metallized and photoresist-coated wafer must first be patterned in order to transfer the interconnection pattern to the photoresist, which is then followed by a dry etch process using chlorine as the primary etch gas to thoroughly remove the metal layer of the chip that is not covered with photoresist.
The remaining photoresist is then removed by dry etching, or wet etching, or both dry etching and wet etching. The next step is to deposit the protected layers of the circuit and components of the chip (passivation). The entire structure of the integrated circuit process will then appear, as shown in the flow chart of FIG. 1.
According to the above process, the conventional aluminum interconnect etching method uses an etch gas composed of chlorine/boron trichloride/nitrogen, or chlorine/boron trichloride/fluoroform. However, due to increased integration and continued shrinking of the line width—for example, to 0.15 mm or less—in semi-conductor components today, the selectivity rate of this etch gas to photoresist and aluminum interconnect stack will not be high enough, thus causing insufficient photoresist to withstand the action of the plasma, which will result in imprecise transfer of patterns. Therefore, the use of conventional photoresist has been gradually replaced by the oxide hardmask. Since there is no photoresist passivation source when using the oxide hardmask, the conventional etch gas made up of chlorine/boron trichloride/nitrogen, or chlorine/boron trichloride/fluoroform—whether it is for controlling the etch remnants or profile—will not be able to generate the precision required by aluminum copper alloy etch in the narrow line width.
Moreover, the current aluminum interconnect etching method, after plasma etching, requires immediate removal of photoresist, Once the photoresist is removed, the chip will be rinsed with water to prevent the corrosion of aluminum copper alloy interconnection by remnants of chlorine and nitrogen. Finally, the wafer needs to be immersed in a cleaning solution to further remove polymers and etch byproducts formed during etching. The wafer has to go through this complicated process before moving into the next processing stage.
In order to overcome the above shortcomings and to simplify the process, this invention introduces a gas formula that works well with the oxide hardmasking method, By taking the advantages of the changes of the major components of the etch gas, this method helps reduce the occurrence of etch remnants and produces better etch profiles. In addition, the invention also uses water vapor plasma during the step of removing etch remnants, which will simplify the complicated process of water rinsing and immersion cleaning after the removal of photoresist, thus allowing the wafer to go directly into the next step for film deposition. As a result, this invention will not only enhance the precision of the transfer of the patterns, but will, due to its simplicity, also shorten production time, reduce production costs, and increase productivity.